Ophthalmic lenses of plastic have become very popular because they are inexpensive, lighter in weight and more resistant to shattering than glass. However, the plastic lenses generally have less surface hardness and wear resistance. Therefore, they are usually coated with abrasion resistant coatings.
The surfaces of lenses made of diethylene glycol bis(allylcarbonate) ("CR-39", a registered trademark of PPG Industries of Pittsburgh, Pa.) or high index polyurethane(HIPU) can be made to be hard and abrasion resistant by the use of abrasion resistant coatings; however, their impact resistance can be greatly reduced by these hard, abrasion resistant coatings, especially in combination with a brittle vacuum deposited antireflective coating. Thin lenses, with a center thickness of about 1.0 mm, are highly desired for cosmetic and weight considerations. However, the thickness of a lens is related to the impact properties of the lens. Specifically, thinner lenses have a lower impact resistance. Plastic lenses that are sold in the United States must meet the requirements of the Food and Drug Administration (FDA), which has specific requirements for the impact properties of a lens.
It would be advantageous to have plastic lenses which are more impact resistant and a method of imparting an impact resisting property that meets or exceeds the FDA requirements for plastic lenses.